This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In a new area of investigation, we are extending our earlier work that combined replica exchange molecular dynamics with the refinement of atomic level structures based on NMR data. In the current efforts, we have utilized chemical shift data alone as a constraint on the refinement of a structural ensemble of the arenavirus Z-protein.